The sunscreen material, 4-(1,1-dimethylethyl)-4'-methoxydibenzoylmethane, known also as Parsol 1789, is supplied by L. Givaudan & Cie Societe, and is described in their GB 2 038 807, as being an outstanding UV A-filter, in that it brings about a considerable retardation in the ageing of the skin with excellent skin tolerance stability (to light, heat and to moisture).
In order to prepare an effective composition to enable a sunscreen material such as this to be applied to the human body surface, particularly to the skin or hair, it is necessary to distribute this sunscreen in a suitable carrier or diluent, at a suitable concentration to facilitate its application at a correct dose over the body surface. The composition so employed must also possess excellent preservative properties, such that the sunscreen material itself does not lose its ability to function as a UV A-filter, and also such that the composition itself is immune from microbial spoilage.
In trade literature issued by Givaudan, the following compatible substances having preservative and antimicrobial compatibility are suggested, (CTFA Designation):
Glutaral PA0 Phenoxyethanol PA0 Chlorhexidine PA0 Propylene Glycol (and) PA0 5-Bromo-5-Nitro-1,3-Dioxane PA0 Methylparaben PA0 Propylparaben PA0 Butylparaben PA0 Triclosan PA0 Methylchloroisothiazolinone (and) PA0 Methylisothiazolinone PA0 Benzalkonium Chloride PA0 Triclocarban
We have carried out extensive trials testing the ability of those from this list which are cosmetically acceptable, but have failed to show that any one, or any combination of them, is sufficiently powerful to preserve some sunscreen compositions containing the sunscreen in question against microbial spoilage, particularly against the effects of yeasts and gram-negative bacteria.
We have also examined the effects of some of the so-called compatible preservative and anti-microbial materials identified by Givaudan in their trade literature, including imidazolidinyl urea (also known as Germall 115) and diazolidinyl urea (also known as Germall II) and have confirmed that the UV A-filter activity of the sunscreen PARSOL 1789 is adversely effected.
The invention is accordingly concerned with the discovery that certain other preservative agents that are not only effective in preserving compositions containing this sunscreen against most microbial spoilage organisms, but also totally compatible with it. Furthermore, these other preservative agents have never been proposed for use with it, either by Givaudan in their trade literature nor in any other source.